Technical Field
This Patent Document relates generally to direct-conversion wireless transceiver design including IQ mismatch compensation.
Related Art
In wireless transceivers, direct conversion can be used for the transmitter (TX) and/or receiver (RX). Direct conversion (zero/low IF) wireless architectures, based on IQ modulation/demodulation and RF upconversion/downconversion, have a number of advantages over IF (heterodyne) architectures.
For wireless base-station applications, the transceiver must meet stringent requirements on out-of-band emission in the transmitter. For this reason, direct conversion transmitter designs use digital compensation for TX non-linearities and IQ mismatch, and include a feedback receiver (FBRX) that captures data required for such compensation.
TX non-linearities are compensated by digital pre-distortion (DPD). IQ mismatch is compensated by digital filtering (IQ mismatch compensation or QMC). To reduce phase noise distortion for DPD processing, the TX LO (local oscillator) and FBRX LO can be generated using the same PLL (phase locked loop).
One approach to achieving acceptable TX DPD and QMC compensation, is to use an IF (rather than direct conversion) FBRX. Such an approach avoids introducing FBRX IQ imbalance into the TX path (i.e., avoiding the requirement for FBRX QMC).
While this Background information references wireless base station application, the Disclosure in this Patent Document is not limited to such applications, but is more generally directed to direct conversion wireless architectures.